The FRP such as CFRP and GFRP using carbon fiber, glass fiber, or aramid fiber as a reinforcing fiber is light and has high durability, and thus is an ideal material for various types of configuring members configuring automobiles, airplanes, and the like.
A typical method for molding the CFRP and the GFRP is an autoclave molding method of pressurizing and heating a laminate, in which a prepreg sheet made of reinforcing fiber and highly toughened epoxy resin is laminated, in an autoclave (pressure vessel) to cure the same.
However, the prepreg sheet generally has a problem in that molding of a complex three-dimensional shape is difficult. Furthermore, as it takes too much material cost and molding time, and the cost becomes high, the application cannot be extended in the present circumstances in the autoclave molding using the conventional prepreg.
In recent years, the Resin Transfer Molding (hereinafter referred to as “resin transfer” or “RTM”) method, vacuum-assisted resin transfer molding method of infusing and impregnating matrix resin by using vacuum pressure, and the like that are inexpensive and can reduce the molding time than the autoclave molding method using the conventional prepreg are given attention as a method of obtaining the CFRP.
Such molding methods are those comprising arranging that in which a dry reinforcing fiber base material not impregnated with matrix resin is laminated in plurals in a molding die, impregnating the matrix resin in the reinforcing fiber base material by infusing low viscosity liquid matrix resin thereto, and thereafter curing the matrix resin by heating in an oven and the like to mold a composite material. Since the dry base material is used in the RTM method, the laminate including the reinforcing fiber base material can be formed in accordance with the complex three-dimensional shape.
In forming the reinforcing fiber base material through such method, a great amount of time is required if forming by laminating the reinforcing fiber base material one at a time, and thus it is required for the forming to arrange the laminate, in which the reinforcing fiber base material is laminated based on a predetermined stacking sequence in advance, in a forming tool. The inter-layers of reinforcing fiber base materials configuring the laminate need to be integrated each other in order to arrange the laminate in the forming tool. If not integrated, the stacking angle and the stacking position of the reinforcing fiber base material may shift in time of movement such as when arranging the laminate in the forming tool even if laminated with the stacking angle and the stacking position controlled in time of lamination. In particular, in the uni-directional reinforcing fiber base material in which the reinforcing fibers are aligned in uni-direction, it is very important to control the stacking angle as the stacking angle greatly influences the characteristics of the fiber-reinforced plastic.
The lamination number of reinforcing fiber base material is sometimes changed in the same member depending on the optimum design of the fiber-reinforced plastic structural parts. For instance, the wing of the airplane and the like have great lamination number and are thick at the root of the wing that bears the main load, but have small lamination number and are thin at the tip of the wing. Reducing the lamination number is generally called the ply drop. In the structural part provided with the ply drop, the position where the reinforcing fiber base material should have ply drops is configured, and thus the stacking position of the reinforcing fiber base material in the laminate is also a very important matter.
Since the prepreg is impregnated with matrix resin, the prepregs are adhered and integrated using the tackiness of the matrix resin. Thus, there is no fear that the stacking angle and the stacking position will shift in the laminate of the prepreg when carried around. However, since the inter-layers of the prepreg are adhered and integrated over the entire surface of the prepreg, wrinkles and the like may produce when forming to a complex shape as described above.
In the laminate of the dry reinforcing fiber base material not impregnated with the matrix resin, resin material such as polyether amine and acrylonitrile-butadiene rubber is arranged on the surface of the reinforcing fiber base material so that the inter-layers of the reinforcing fiber base material can be adhered and integrated through the resin material, as described in patent document 1 and the like. However, patent document 1 does not disclose the adhesion mode of the inter-layers in the laminate of the reinforcing fiber base material; if the inter-layers are adhered and integrated over the entire reinforcing fiber base material in the laminate of the dry reinforcing fiber base material, formation to a complex shape is difficult similar to the laminate of prepreg, and the advantages of formability obtained as the matrix resin is not impregnated cannot be exhibited.
Patent document 2 discloses using the reinforcing fiber base material in which the adhesive resin, in which glass transition temperature Tg is between 0 and 95° C., is attached over the entire surface of the base material in dot-form, linear form, or discontinuous linear form on at least one side of a reinforcing fiber sheet, and adhering and integrating the reinforcing fiber base material with the adhesive resin. In other words, patent document 2 describes that the adhesion condition of the laminate is that the temperature is within a range of Tg to (Tg+50° C.), the pressure is lower than or equal to 0.1 MPa, and the time is within three hours, and that when adhered in such condition, the adhesive resin appropriately melts over the entire reinforcing fiber base material and the variation by places of the adhesive strength of the reinforcing fiber base materials is small. However, as the inter-layers are adhered and integrated over the entire reinforcing fiber base material even in the technique described in this document, the formation to the complex shape is also difficult similar to the laminate of prepreg, and the advantages of formability obtained as the matrix resin is not impregnated cannot be exhibited.
Patent document 3 describes a method of arranging a press tool having a pressing portion capable of heat sealing in a lattice-form attached to a press machine on the laminate of the reinforcing fiber base materials, and heating and pressurizing for a constant time the laminate under a heating atmosphere of 80° C. to join the inter-layers of the reinforcing fiber base materials. However, this document does not describe the method of controlling the pressure of each pressing portion. Thus, when adhesion of the large laminate such as one used in a large member including airplane members, it is very difficult to uniform the pressure of all pressing positions and maintain such pressure for a constant time.
In addition, patent document 3 describes a mode in which the stacking sequence (lamination number and the like) of the reinforcing fiber base material is the same over the entire laminate and the thickness of the laminate is substantially constant, but the stacking sequence of the reinforcing fiber base material may differ depending on the site even in one member, and the thickness of the laminate may differ depending on the site. If the thickness of the laminate differs depending on the site, when pressed using the press tool in which a plurality of pressing pins are completely fixed to one plate as described in FIG. 5 of patent document 3, the pressing pin impinges the thick site of the laminate while the pressing pin is less likely to impinge the thin site of the laminate, whereby pressurization with an even pressure over the entire laminate is difficult; as a result, even adhesion cannot be realized. If the pressure is too high, the adhesion of the inter-layers at such site becomes strong, and drawbacks such as generation of wrinkles become a concern in time of forming. If the pressure is too low, the adhesion of the inter-layers at such site becomes weak and the inter-layers delaminate in handling before forming, whereby drawbacks such as degrading of handling property become a concern. Therefore, the press tool having a mechanism in which each pressing pin can independently control the pressure is desired.
In other words, although a technique of improving the handling property, and adhering and integrating the inter-layers to express satisfactory formability when collectively forming to a predetermined shape, and a manufacturing device for manufacturing such laminate are desired in the laminate of the dry reinforcing fiber base material not impregnated with matrix resin, they are not achieved in the present circumstances.    Patent document 1: Japanese Laid-Open Patent Publication No. 8-300395    Patent document 2: Japanese Laid-Open Patent Publication No. 2004-114586    Patent document 3: Japanese Laid-Open Patent Publication No. 2006-103305